Thanks once more, I'm quite impressed with the replies and level of understanding on the forum.

My limited experience running the Nimble has been very positive. Early testing was done by two of my printer gurus, Michael Hackney (positive remarks are on his blog, Sublime Layers) and Simon Khoury of Precision Piezo, both running deltas on Duet controllers. Apparently the primary bottleneck in the extruder's performance appears to be the retract speed which in Simon's experience was limited to about 30mm/s but has thus far proven workable. I'm looking forward to running a delta with its Achilles heel having been removed. In any case I'm no speed demon, I'm fine taking as long as needed to get nice-looking prints.

I'll be using the Duet control board myself so no problem keeping up with the math.

And thanks much for the tip on thermistor installation!

You're certainly correct, only direct experience will decide things for sure, so the V4 was ordered this morning. The responses which I've gotten here helped greatly to clear up a few questions and to encourage me to go ahead with the scheme.

Being a brutalist kind of guy, I'd skip the fancy cylinders-on-ribs-with-fillets and go for a triangular-ish flat plate, but your design definitely wins on stylin'.

Thanks, and yeah I know ... I tend to indulge my love of industrial design when I build these things. But for the initial temp testing once I've received the V4 I'll just throw on a plate as you suggest.

insta wrote:And, sthone, I actually added my fans back in. I *think* it made the printer more reliable, but it's certainly not incredibly noticable one way or another.

I still don't understand the point of the extruder fan or what it's suppose to be for. I get back in the day they kept the heat from traveling up the longer hot ends but now with the V4 that's not even possible and the fan just points at the filament drive and extruder gear. The only thing I can see it accomplishing is cooling the stepper motor maybe? Anyone want to enlighten me on it's function nowadays?

As far as I know you're quite correct sthone, though in fact from most peoples' perspectives we are still "back in the day"! The V4 uses a design which I'd never come across before, with its fragile but essential little heat break and the way it's been physically de-coupled from the extruder above it this hot end manages heat dissipation in a very novel way.

The only reason I had tentatively allowed the inclusion of a very small fan was that I'd guessed that without the mass of the rather large mounting bracket some of this utility may fail to be realized, but from the sound of things it will not have to be there -- which would be great! When the unit arrives tomorrow, first thing I'll do is run it up to temperature and, by inserting a secondary thermistor into the mounting bracket very near the interface, monitor the thermal behavior as the temps increase.

One thing I've noticed recently is that even with the extruder fan running until the V4 cools down to 50C, the PLA I am using continues to melt a bit. After everything cools down, instead of seeing the full width of the filament going down into the hot end, it's often necked down to a much thinner width. This is with eSun PLA+, and I've been running the extruder at the top of the PLA+ temperature range (225C). Because the filament is usable down to 205C (and will probably still flow a bit below that), it apparently oozes/sags a bit while the hot end cools down. Without a fan, I suspect things could be much worse. It doesn't appear to affect anything, but it shows that the heat is creeping up into the filament drive at least a bit.

Thanks again for the input Gwhite. Yes, it was from having seen another post on this forum -- with a photo showing heat creep and molten filament there at the top end of the V4 -- that some of my concern arose regarding the V4's suitability in this application I've got in mind (for which it was never intended). And indeed, should this prove to be a problem it's most likely to raise its head when printing PLA.